asp.net-mvc - Asp.Net MVC - 模型绑定(bind)到模型或 ViewModel

Question

我有一个 Controller ，它返回一个传入 View 模型的 View ，该 View 模型具有显示 View 所需的属性(下拉选择项列表等)。

但是当我将它发布到服务器时，我有一个不同的模型类，它具有那些下拉列表的选定值。在我的 HttpPost Controller 操作中，我在进行任何处理之前检查了 (ModelState.IsValid)，但是当它为 false 时，我“返回 View(model)”。

但由于 View 绑定(bind)到 ViewModel，而我的 Post 操作正在接受实际模型，我收到错误消息“传递到字典中的模型项的类型为“模型”，但该字典需要“ViewModel”类型的模型项，当我提交表单时，验证错误会显示在 View 上。

我该如何解决这个问题？使用强类型 View 、传入 View 模型但提交到不同模型时的最佳实践是什么？

代码:

 public ActionResult Buy()
    {
      BuyVM buyVM = GetBuyVM();
      return View(buyVM);
    }

   [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Buy(BuyModel model)
    {
      if (ModelState.IsValid)
        {
        // Do Procesing
        return View("Success");
        }
      return View(model);
    }

 public class BuyVM
    {
        public SelectList PurchaseDateList { get; set; }

        public SelectList BedroomsList { get; set; }

        public SelectList StoriesList { get; set; }

        [Required]
        public string SquareFootage { get; set; }

        [Required]
        public string PreferredCityLocations { get; set; }

        public string AdditionalInfo { get; set; }
    }

 public class BuyModel 
    {
        public string PurchaseDateList { get; set; }
        public string BedroomsList { get; set; }
        public string StoriesList { get; set; }
        public string SquareFootage { get; set; }
        public string PreferredCityLocations { get; set; }
        public string AdditionalInfo { get; set; }
    }

 private static BuyVM GetBuyVM()
        {
            BuyVM buyVM = new BuyVM();

            buyVM.PurchaseDateList = new SelectList(new[] { "Immediately", "1 to 3 months", "4 to 6 months", "More than 6 months" });
            buyVM.BedroomsList = new SelectList(new[] { "1", "2", "3", "4", "5+" });
            buyVM.StoriesList = new SelectList(new[] { "1", "2", "Does not matter" });

            return buyVM;
        }

购买.cshtml

    @model Models.BuyVM
    // html
 @Html.DropDownListFor(m => m.PurchaseDateList, Model.PurchaseDateList, new { @class = "form-control" })

 @Html.DropDownListFor(m => m.BedroomsList, Model.BedroomsList, new { @class = "form-control" })

因此，当我返回 View (模型)时，如果存在验证错误 (JQueryVal)，在 HTTPPost 中，如果我将模型传递回 View ，我将尝试显示验证错误。但是我有这种类型不匹配。

Answer 1

首先，您的数据模型名称没有意义。名为 BedroomsList 的属性表示 Bedrooms 的集合，但该属性是一个 string。首先为您的属性命名以描述它们是什么，以便其他人可以理解您的代码。

public class BuyModel 
{
  public string PurchaseDate { get; set; }
  public string Bedrooms { get; set; }
  public string Stories { get; set; }
  public string SquareFootage { get; set; }
  public string PreferredCityLocations { get; set; }
  public string AdditionalInfo { get; set; }
}

相应的 View 模型需要包含这些属性以及 SelectList 属性。

public class BuyVM
{
  public string PurchaseDate { get; set; }
  public string Bedrooms { get; set; }
  public string Stories { get; set; }
  [Required]
  public string SquareFootage { get; set; }
  [Required]
  public string PreferredCityLocations { get; set; }
  public string AdditionalInfo { get; set; }
  public SelectList PurchaseDateList { get; set; }
  public SelectList BedroomsList { get; set; }
  public SelectList StoriesList { get; set; }
}

接下来删除您的 GetBuyVM() 方法并将其替换为 Controller 中填充选择列表的方法，这样您也可以在 ModelState 无效时调用该方法并且您需要返回 View 并将 POST 方法更改为 View 模型的参数(您的 View 基于 BuyVM 因此您必须回发到 BuyVM，而不是 BuyModel)

public ActionResult Buy()
{
  BuyVM model = new BuyVM(); // initalise an instance of the view model
  ConfigureViewModel(model);
  return View(model);
}

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Buy(BuyVM model)
{
  if (!ModelState.IsValid)
  {
    ConfigureViewModel(model);
    return View(model);
   }
   Initialize your data model and map the view model properties to it
   BuyModel dataModel = new BuyModel()
   {
     PurchaseDate = model.PurchaseDate,
     Bedrooms = model.Bedrooms,
     ....
   };
   // save the data model
   return View("Success");
}

private ConfigureViewModel(BuyVM model)
{
  model.PurchaseDateList = new SelectList(new[] { "Immediately", "1 to 3 months", "4 to 6 months", "More than 6 months" });
  model.BedroomsList = new SelectList(new[] { "1", "2", "3", "4", "5+" });
  model.StoriesList = new SelectList(new[] { "1", "2", "Does not matter" });
}

最后在 View 中，绑定(bind)到您的属性(PurchaseDate，而不是 PurchaseDateList)

@Html.DropDownListFor(m => m.PurchaseDate, Model.PurchaseDateList)
@Html.DropDownListFor(m => m.Bedrooms, Model.BedroomsList)